Enable upgrades from a mod_nss-installed master to mod_ssl
    
    The existing private/public keys are migrated to PEM files
    via a PKCS#12 temporary file. This should work for both
    IPA-generated and user-provided server certificates.
    
    Related: https://pagure.io/freeipa/issue/3757
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>